1. Technical Field of the Invention
The present invention relates to a headlight lighting angle control apparatus for controlling lighting angle of headlights installed in a vehicle.
2. Related Art
The technique of this art has been well known as disclosed, for example, in Japanese Patent Application Laid-Open Publication No. 2003-072460. The technique disclosed in this literature uses wheel speed which is detected by a wheel speed sensor for detecting wheel speed of the vehicle, and steering angle which is detected by a steering angle sensor for detecting steering angle of the steering wheel of the vehicle. Based on the wheel speed and the steering angle, the lighting angle of the headlights is controlled so that a point estimated to be reached by the vehicle after the expiration of a predetermined time interval, will fall within a range lit by the headlights of the vehicle.
It is true that, in the headlight lighting angle control apparatus mentioned above, the lighting angle of the headlights is controlled so that the point estimated to be reached by the vehicle after the expiration of a predetermined time interval, will fall within a range lit by the headlights of the vehicle. However, since the headlight lighting angle is determined based on the wheel speed and the steering angle, the timing for actually starting control of the headlight lighting angle falls immediately before the vehicle actually enters a curve, that is, falls after the vehicle has reached a point quite close to a starting point of the curve. Generally, a vehicle driver visually confirms in advance the depth, sharpness or the like of a curve before turning the steering wheel, or just before the vehicle actually goes around the curve. Accordingly, when taking a drive at night, an attempt to visually confirm the depth or sharpness of a curve just before the vehicle actually goes around the curve will ends up in vain because the curve is yet to be lit by the headlights. Thus, during nighttime driving, it is difficult for a vehicle driver to visually confirm in advance the line shape of a curve the vehicle is going to enter.